Lighting fixture with selectable color temperature

ABSTRACT

A lighting fixture for powering multiple LED groups to generate a selectable color temperature. The lighting fixture provides varying amounts of power to each group of LEDs to achieve a selected color temperature. Current from a driver may be divided between the LED groups based on a selected operational state, which is selected using a switch or other configurable input. The operational states may turn the LED groups on or off or may control an amount of current received by the LED groups. In some configurations, all of the LED groups are always at least partially powered.

RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 16/860,626, which is adivisional of U.S. Pat. No. 10,674,579, which claims priority to aprovisional application entitled Lighting Fixture with Selectable ColorTemperature, U.S. Ser. No. 62/622,275. This application is also relatedto U.S. Pat. No. 10,601,874, which a divisional of U.S. Pat. No.10,674,579. All of the foregoing are incorporated by reference herein intheir entirety.

TECHNICAL FIELD

This disclosure relates generally to the field of lighting fixtures.More specifically, this disclosure relates to controlling power tomultiple groups of LEDs to produce different color temperatures using asingle fixture.

BACKGROUND

Lighting fixtures can produce different color temperatures of whitelight to suit the preferences of different consumers or activities. Forexample, a cool white light may be preferred by some consumers orappropriate for some activities, whereas a warm white light may bepreferred by other consumers or appropriate for other activities. Insome instances, different light fixtures are required to provide lightwith different color temperatures.

SUMMARY

The present invention is directed to systems and methods for selecting acolor temperature by controlling the power provided to multiple groupsof LEDs. Each group of LEDs may individually provide light at adifferent color temperature. A lighting system may provide varyingamounts of power to each group of LEDs to achieve a selected colortemperature.

In some examples, the fixture may use a single driver output or currentsource to power all of the LED groups in the lighting fixture. Thecurrent is divided between the LED groups based on a selectedoperational state. The operational state may be selected using a switchor other configurable input. The operational states may turn the LEDgroups on or off or may control an amount of current received by the LEDgroups. In some configurations, all of the LED groups are always atleast partially powered. In some examples, a multi-channel driver isused. In those cases, each LED group is connected to a differentchannel.

In some examples, the LED groups are controlled to provide discretecolor temperature points, i.e., stepped control, and in other examples,the LED groups are controlled to provide a continuous range of colortemperatures, i.e., continuous control.

These and other aspects of the invention will be described in moredetail and in the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, embodiments, and advantages of the present disclosure arebetter understood when the following Detailed Description is read withreference to the accompanying drawings, where:

FIG. 1 depicts an example of a circuit for controlling LED groups usingbleed resistors, according to the present disclosure.

FIG. 2 depicts an example of a circuit for controlling LED groups usingbleed resistors, according to the present disclosure.

FIG. 3A depicts an example of a circuit for controlling LED groups usinga multi-channel driver, according to the present disclosure.

FIG. 3B depicts an example of a circuit for controlling LED groups usinga multi-channel driver, according to the present disclosure.

FIG. 4 depicts an example of a circuit for controlling LED group using asingle selector switch, according to the present disclosure.

FIG. 5 depicts an example of a circuit for controlling LED groups usinga potentiometer, according to the present disclosure.

FIG. 6 depicts an example of current levels for LED groups, according tothe present disclosure.

DETAILED DESCRIPTION

Briefly described, the present disclosure generally relates to alighting fixture that controls current to multiple LED groups to producedifferent color temperatures. The fixture controls current to each ofthe LED groups so that the fixture produces light with a colortemperature that corresponds to the color temperature of one of the LEDgroups or a color temperature that corresponds to a combination of thecolor temperatures of multiple LED groups.

In some configurations, the fixture may use a single driver output orcurrent source to power all of the LED groups in the lighting fixture. Aselected operational state determines how the current is divided betweenthe LED groups. A switch or other configurable input selects theoperational state. In one configuration, the fixture provides a firstamount of current to an LED group so that the LED group is fully oralmost fully powered and produces light at or near its full intensity,and provides a second amount of current, which is smaller than the firstamount of current, to another LED group so that the other LED group ispartially powered and produces light at less than its full intensity. Inthis configuration, the current provided to each LED group is based onthe state of a switchable path between the driver and the LED group anda bleed resistor connected in parallel to the switchable path. In thisconfiguration, the fixture provides light at color temperatures betweenthe color temperatures of the individual LED groups.

In another configuration, the fixture provides current to one of themultiple LED groups so that one LED group is powered at a time. A switchor other input selects which one of the LED groups is powered. In thisconfiguration, the fixture provides light at color temperatures thatcorrespond to the color temperature of the individual LED groups.

In another configuration, the fixture divides the current to the LEDgroups based on a potentiometer. A current control circuit is connectedto each LED group and controls the amount of current to its LED groupbased on the value of the output of the potentiometer. The fixtureprovides light at color temperatures that correspond to the colortemperatures of each of the LED groups, as well as color temperaturesbetween the color temperatures of the LED groups.

In other configurations, the fixture may use a multi-channel driver ormultiple current sources to power the LED groups so that each LED groupis connected to a different channel or current source. A switchingdevice controls the driver channels or current sources to control thecurrent provided to the LED groups. The fixture may provide light atcolor temperatures between the color temperatures of the individual LEDgroups.

An LED group may include multiple LEDs. The LEDs in an LED group may beconnected in series, in parallel, or in any combination thereof.Individual LEDs in an LED group may have the same color temperature ormay have different color temperatures. The number of LEDs in an LEDgroup may differ between LED groups within the same lighting fixture.When the LED group is powered, the LEDs collectively provide light at acolor temperature. The disclosure is also applicable to lightingfixtures that use other types of lighting elements including, but notlimited to, OLEDs.

Fixture with Bleed Resistors

Referring now to the figures, FIG. 1 depicts an example of a circuit forcontrolling two LED groups that includes bleed resistors, according tothe present disclosure. A circuit 100 controls multiple groups of LEDs.The circuit 100 is connected to an output of a driver (not shown) and aground or a driver return 116. The circuit 100 includes a first bleedresistor 104 and a second bleed resistor 106. The first bleed resistor104 is connected between the driver output and the first group of LEDsand the second bleed resistor 106 is connected between the driver outputand the second group of LEDs. The bleed resistors may have the samevalue or different values. In one example, both of the bleed resistorsare 1K Ohms.

Each LED group contains a plurality of LEDs, such as LEDs 112A, 112B,112C, collectively referred to as the “first LED group” 112, or LEDs114A, 114B, 114C, collectively referred to as the “second LED group”114. The first LED group 112 may include a number of LEDs 112A, 112B,and 112C that collectively produce light with a color temperature of2700K. The second LED group 114 may include a number of LEDs 114A, 114B,and 114C that collectively produce light with a color temperature of5000K. Color temperatures of 5000K and above are generally considered“cool colors”, and color temperatures between 2000K-3000K are generallyconsidered “warm colors”.

The output of the driver is connected to the first bleed resistor 104,the second bleed resistor 106, and a switching device 107. FIG. 1illustrates that the switching device has two switches and that thefirst switch 108 is parallel to the first bleed resistor 104 and thesecond switch 110 is parallel to the second bleed resistor. Otherconfigurations for the switching device are also possible. The switchingdevice provides a switchable path between the output of the driver andeach of the LED groups. The switching device may enable operationalstates that produce light at a selectable color temperature. The On-Offswitching of the fixture and any dimming control is provided by anothercontroller or circuit, which is not shown in FIG. 1. The dimming controlcan, in some configurations, be provided by a constant current driverthat varies the total current supplied to the LED groups. Dimming isprovided by controlling the amount of current provided by the driver.The proportion of the current provided to each LED group is the same forall intensities

In a first exemplary state, the first switch 108 is open and the secondswitch 110 is closed so that the second LED group 114 is connected tothe driver output via closed second switch 110 and the second bleedresistor 106. The circuit 100 provides a first amount of current to LEDgroup 114 and a second amount of current to LED group 112. The firstamount of current is greater than the second amount of current. Thesecond amount of current is sufficient to partially power LED group 112so that it produces light. The first LED group 112 is connected to thedriver output only via the first bleed resistor 104 since the firstswitch 108 is open. The combination of the more fully powered LED group114 and the partially powered LED group 112 generates light with a colortemperature with a measurable and perceptible color temperature shiftfrom 5000K.

For example, assume the driver produces 9 W of power and LED groups 112and 114 each have enough 3V LED's to create LED strings of 27V each. Theresultant current output under this configuration will be 333 mA (27multiplied by 0.333 equals 9). If the partially powered LED group 112has a bleed resistor set at 818 ohms then the resultant currenttraveling through the string will be 33 mA (27 divided by 818 equals0.033). Given that the driver is of a constant current configuration at333 mA and that partially powered LED group 112 is consuming 33 mA thenthe more fully powered LED group 114 will receive around 300 mA ofcurrent. This will result in a 90:10 distribution of current betweenpartially powered LED group 112 and more fully powered LED group 114.Assuming LED group 112 and LED group 114 are populated with LEDs withefficacies of 200 lumens per watt then a singular LED in the more fullypowered LED group 114 will produce around 60 Lumens (200 multiplied by0.3 equals 60) while an LED in partially powered LED group 112 willproduce 6.6 lumens (200 multiplied by 0.033 equals 6.6). Given thatlight of different colors and intensities mix to form new combinedcolors those skilled in the art may appreciate that a color temperatureshift occurs when partially powered LED group 112 produces light at2700K and more fully powered LED group 114 produces light at 5000K. At a90:10 ratio 90% of the light will be at 5000K and 10% of the light willbe at 2700K. The color temperature difference between the two is 2300(5000 minus 2700 equals 2300). Ten percent (10%) of 2300 is 230 so theresultant color temperature will be 4770K (5000−230). These values are afirst approximation. Other ratios of currents may also be used and thecurrent may be divided between more than two LED groups.

When there are two LED groups, the ratio of the light output by one ofthe LED groups to the light output by the other LED group may fall in arange from 96:4 to 60:40. Typically, a color temperature shift above100K is perceptible by the human eye, so some implementations shift thecolor temperature by between 4% and 40%. There are also more preciseformulas to determine the exact shift based on the xy values of the LEDcolor as measured under the CIR 1931 chromaticity chart.

In a second exemplary state, the first switch 108 is closed and thesecond switch 110 is open. First LED group 112 is connected to thedriver output via closed first switch 108 and the first bleed resistor104. The circuit 100 provides a first amount of current to LED group 112and a second amount of current to LED group 114. The first amount ofcurrent is greater than the second amount of current. The second amountof current is sufficient to partially power LED group 114 so that itproduces light. LED group 114 is connected to the driver output only viathe second bleed resistor 106 since the second switch 110 is open. Thecombination of the more fully powered LED group 112 and the partiallypowered LED group 114 generates light with a color temperature with ameasureable and perceptible color temperature shift from 2700K.

In a third exemplary state, the first switch 108 is closed and thesecond switch 110 is closed. The circuit 100 provides current to LEDgroup 112 and to LED group 114 to more equally power both LED groups. Insome situations, the amount of current provided to the LED groups issubstantially the same. The combination of the outputs of LED group 112and LED group 114 generates light with a color temperature between 5000Kand 2700K.

A fourth exemplary state is optional and depending on the driverconfiguration may not be practical. In this state, the first switch 108is open and the second switch 110 is open. LED group 112 is connected tothe driver output via first bleed resistor 104 and LED group 114 isconnected to the driver output via the second bleed resistor 106. Insome situations, the amount of current provided to the LED groups issubstantially the same in this state but lower than in the previousstates. The combination of the powered LED group 112 and the powered LEDgroup 114 generates light with a color temperature between 5000K and2700K.

FIG. 2 depicts another example of a circuit that uses bleed resistors.In this example, the circuit includes a controller 202 that controls twoswitches 205 and 207. A first bleed resistor 204 is connected inparallel with the first switch 205 and a second bleed resistor 206 isconnected in parallel with the second switch 207. The first bleedresistor 204 and the first switch 205 are connected to a first LED group208. The second bleed resistor 206 and the second switch 207 areconnected to the second LED group 210. The controller controls theswitches to provide operating states similar to those described above inconnection with FIG. 1.

Although FIGS. 1 and 2 illustrate two groups of LEDs, other examples mayuse three or more groups of LEDs and may control the groups of LEDs sothat at least one of the groups of LEDs is connected to the output of adriver through a closed switch and its respective bleed resistor and atleast one of remaining groups of LEDs is connected to the output of thedriver only via its respective bleed resistor.

Fixture with Multi-Channel Driver

In other examples, the fixture uses a driver with multiple outputchannels. FIG. 3A depicts an example of a circuit for controlling LEDgroups using a multi-channel driver, according to the presentdisclosure. The multi-channel driver 306 has a first channel connectedto first LED group 308 with LEDs 308A-308C, and a second channelconnected to second LED group 310 with LEDs 310A-310C. The multi-channeldriver 306 additionally has a switching device connected to inputs ofthe driver. In FIG. 3A, the switching device includes a first switch 302and a second switch 304 and each switch is connected to an input of thedriver. The positions of the first switch 302 and the second switch 304control the inputs of the driver and accordingly the state of the outputchannels. The multi-channel driver 306 may be configured to provide apre-programmed current on each channel based on a setting of the firstswitch 302 and the second switch 304.

FIG. 3B depicts another example of a circuit for controlling LED groupsusing a multi-channel driver, according to the present disclosure. Themulti-channel driver 306 has a first channel connected to a first LEDgroup 308 with LEDs 308A-308C, and a second channel connected to asecond LED group 310 with LEDs 310A-310C. A switching device isconnected to an input of the driver. In FIG. 3B the switching deviceincludes a controller 312, a first switch 302, and a second switch 304.The positions of the first switch 302 and the second switch 304 controlinputs of the controller and are used to determine the input to thedriver. The driver controls the state of the output channels based onthe input. The multi-channel driver 306 may be configured to provide apre-programmed current on each channel based on the output of thecontroller 312.

In one configuration, the first LED group 308 is connected to a firstchannel of the multi-channel driver 306 and the second LED group 310 isconnected to a second channel of the multi-channel driver 306. Thedriver in FIG. 3A or the combination of the driver and the controller inFIG. 3B may be configured so that the driver provides a pre-programmedamount of output current based on the state of the switching device thatcontains the first switch (S1) and the second switch (S2). In thisexample, the multi-channel driver 306 provides 1000 mA of output currentdivided between two output channels (i.e., Channel 1 and Channel 2) asshown in Table 1 below.

TABLE 1 Color Color Resulting Tem- Tem- Color Channel Channel peratureperature Tem- S1 S2 1 2 Channel 1 Channel 2 perature On Off 900 mA 100mA 5000K 2700K 4770K Off On 100 mA 900 mA 5000K 2700K 2930K On On 500 mA500 mA 5000K 2700K 3850K

As shown in Table 1, the switching device containing the first switchand the second switch has at least three potential states, each statebased on a particular configuration of the switches. As previouslydescribed, in states where at least one of the first switch or secondswitch is in a “closed/on” position, both channel 1 and channel 2 are atleast partially powered. In a state with both the first switch and thesecond switch in “closed/on” positions, the current provided by themulti-channel driver 306 is split between channel 1 and channel 2.Although Table 1 shows that the current is split evenly between channel1 and channel 2 when both switches are in the “closed/on” positions andthat the same current levels are provided on each channel, otherdivisions of current are also possible. For example, the output levelsfor channel 1 may differ from the output levels for channel 2. If thefixture provides a state where both switches are allowed to be in the“open/off” state, then the driver may not provide current to eitherchannel or may provide current according to a fourth predefined state.Although Table 1 illustrates that the switching device includes twoswitches, the switching device may provide three states using adifferent number of switches or different types of components.

Fixture with Single Selector

Other types of switching devices may be used to select one LED groupfrom multiple LED groups so that only one LED group is powered at atime. FIG. 4 depicts an example of a circuit 400 with multiple LEDgroups, an LED driver, and a switching device. In this example, theoutput of the LED driver 402 is selectively connected to LED group 408with LEDs 408A-408C or to LED group 410 with LEDs 410A-410C based on thestate of switching device 412. The switching device may be a singleselector switch. In one example, LED group 408 may produce light with acolor temperature of 5000K and LED group 410 may produce light with acolor temperature of 2700K. The LED driver 402 provides output to LEDgroup 408 or LED group 410 based on the setting of the single selectorswitch 412 as shown in Table 2 below.

TABLE 2 Switch LED group 408 LED group 410 Position 1 800 mA  0 mAPosition 2  0 mA 800 mA

In this configuration, the single selector switch 412 controls which oneof the LED groups receive power from the LED driver 402. The singleselector switch 504 may have more than the two positions shown in Table2 and if so, then both LED groups will be off in the additionalpositions.

In an alternative or additional configuration, the circuit 400 mayinclude more than two LED groups. In an example using three LED groups,the LED groups may provide light at color temperatures of 5000K, 4000K,and 2700K respectively. In this configuration, the single selectorswitch 412 controls which one of the LED groups receive power from theLED driver 402. The circuit 400 provides one of the LED groups receivingpower based on the position of the single selector switch 504 with theother LED groups not receiving power from the LED driver 402.

Fixture with Potentiometer

In other examples, a potentiometer may be used to control the colortemperature by controlling current through the LED groups. FIG. 5illustrates an exemplary circuit for controlling LED groups using apotentiometer, according to the present disclosure. In this example, theoutput of the LED driver 502 is connected to a first LED group 508 withLEDs 508A-508C and a second LED group 510 with LEDs 510A-510C). Thecircuit 500 controls power provided to the first LED group 508 andsecond LED group 510 based on the output of a potentiometer 512. A firstcurrent control circuit 504 is connected to the first LED group and thepotentiometer 512. A second current control circuit 506 is connected tothe second LED group and the potentiometer 512. The potentiometer 512controls the first current circuit 504 and the second current controlcircuit 506 based on the output of the potentiometer.

In one configuration, the potentiometer provides a voltage signal whichvaries between 0-5V and which may be connected to a pulse widthmodulation (PWM) circuit. The PWM in turn drives a MOSFET-type oftransistor. The transistors are then wired in series with each LEDGroup. In this configuration as the pulse width varies from 0% to 100%the resultant current flowing through the first LED group will vary from0% to 100%. A second PWM circuit connected in reverse to the second LEDgroup will result in the resultant current flowing through the secondLED group to vary from 100% to 0%. This will result in the desiredbehavior between the two LED groups.

In another embodiment, FETs may be connected in series with each of theLED groups. In this scenario, the potentiometer provides a varyingvoltage to the FET controller that in turn drives each FET in the linearregion. This configuration makes the FETs act like a current controllerto each LED group. By connecting each FET in reverse configuration, LEDgroup 1 will see a rise in current when the potentiometer transitionsfrom 0 to 5 V while LED group 2 will see a decrease in current when thepotentiometer transitions from 0-5V.

In another embodiment, step functions may be provided by either theFET's or the MOSFET circuits by only allowing the output of the PWM tochange when a particular voltage is output by the potentiometer. As anexample, 0-2V may vary the CCT change on a 90:10 ratio while 2-4V mayvary the CCT in a 50:50 ratio. The same can be done with the linear FETcircuit by providing hysteresis to the circuit driving the linear FET's.

In one configuration, the circuit 500 provides stepped control based onthe output of the potentiometer. Stepped control allows selection ofcertain predetermined color temperatures. The first current controlcircuit 504 and the second current control circuit 506 each includetransistors that provide a switching function and turn the first LEDgroup 508 and the second LED group 510 on and off as shown below inTable 3. Table 3 illustrates a fixture with three possible colortemperature selections.

TABLE 3 Potentiometer LED LED Output Transistor 1 Transistor 2 Group 508Group 510 0 V Off On Off On 1.5-3.5 V On On On On 3.6-5 V On Off On Off

In another configuration, the circuit 500 provides continuous controlbased on the output of the potentiometer. Continuous control allowsselection of a range of color temperatures between the colortemperatures of each individual LED group. The current control circuitsin this configuration slowly shift the current and provide continuouscontrol of the color temperature produced by the combination of thefirst LED group 508 and the second LED group 510. The color temperaturemay vary in continuous values of color temperature as the current variesas shown in FIG. 6.

FIG. 6 illustrates that when the potentiometer output is at its minimumvalue, e.g., 0V, that LED group 1, i.e., LED group 508, receives no or aminimum level of current and LED group 2, i.e., LED group 510 receives amaximum level of current. As the potentiometer output increases from itsminimum value, the amount of current received by the first LED groupincreases and the amount of current received by the second LED groupdecreases. The first LED group and the second LED group may both bepartially powered, but may receive different amounts of current based onthe output of the potentiometer. When the potentiometer output is at itsmaximum value, e.g., 5V, LED group 1 receives the maximum level ofcurrent and LED group 2 receives no or a minimum level of current.

Some fixtures may include a potentiometer with detents to assist in theselection of the color temperature. For example, when a first detent ofthe potentiometer is engaged, the fixture may generate a firstpredetermined color temperature that is a combination of the colortemperatures of two or more LED group and when a second detent of thepotentiometer is engaged, the fixture may generate a secondpredetermined color temperature that is a different from the first andis a different combination of the color temperatures of two or more LEDgroups.

General Considerations

The color temperatures, number of LED groups, number and arrangements ofLEDs in an LED group, and currents used in the above examples areexemplary. Other implementations may use different values, numbers, orarrangements and may use other types of lighting elements. The fixturemay be any type of a fixture, including a linear fixture, a downlight,or a flush mount fixture. The LEDs of the different LED groups may bearranged so that the LEDs from different groups are interspersed in thefixture or may be arranged so that LEDs from different groups areseparated in the fixture. Other light characteristics other than colortemperature may also be changed or controlled.

A switching device may use any type of component or combination ofcomponents to provide the described states or switching functions. Aswitching device may include any type of mechanical, electrical, orsoftware switch and a switch may be controlled or set directly orindirectly. A switch may be controlled by a user or by another componentthat is either part of the fixture or remote from the fixture.

Although the foregoing describes exemplary implementations, otherimplementations are possible. It will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily produce alterations to, variations of, and equivalents to thedescribed aspects. Accordingly, it should be understood that the presentdisclosure has been presented for purposes of example rather thanlimitation and does not preclude inclusion of such modifications,variations, and/or additions to the present subject matter as would bereadily apparent to one of ordinary skill in the art.

Unless specifically stated otherwise, it is appreciated that throughoutthis specification discussions utilizing terms such as “processing,”“computing,” “calculating,” “determining,” and “identifying” or the likerefer to actions or processes of a computing device, such as one or morecomputers or a similar electronic computing device or devices, thatmanipulate or transform data represented as physical electronic ormagnetic quantities within memories, registers, or other informationstorage devices, transmission devices, or display devices of thecomputing platform.

The use of “adapted to” or “configured to” herein is meant as open andinclusive language that does not foreclose devices adapted to orconfigured to perform additional tasks or steps. Additionally, the useof “based on” is meant to be open and inclusive, in that a process,step, calculation, or other action “based on” one or more recitedconditions or values may, in practice, be based on additional conditionsor values beyond those recited. Headings, lists, and numbering includedherein are for ease of explanation only and are not meant to belimiting.

What is claimed is:
 1. A lighting fixture, comprising: a driver with atleast two output channels for powering a first LED group and a secondLED group, wherein the first LED group is connected to a first outputchannel and the second LED group is connected to a second outputchannel; the first LED group configured to provide light output at afirst color temperature; the second LED group configured to providelight output at a second color temperature, which is different than thefirst color temperature; and a switching device connected to at leastone input of the driver, wherein the switching device provides at leastthree states, so that: when the switching device is in a first state,current provided by the first output channel to the first LED group isat a first maximum level and current provided by the second outputchannel to the second LED group is at a second minimum level; when theswitching device is in a second state, current provided by the firstoutput channel to the first LED group is at a first interim level andcurrent provided by the second output channel to the second LED group isat a second interim level; and when the switching device is in a thirdstate, current provided by the first output channel to the first LEDgroup is at a first minimum level and current provided by the secondoutput channel to the second LED group is at a second maximum level. 2.The lighting fixture of claim 1, wherein the switching device comprisesa controller and the controller determines the state of the switchingdevice based on inputs to the controller.
 3. The lighting fixture ofclaim 1, wherein the switching device comprises at least a first switchand a second switch and an output of each switch is connected to aninput to the driver, wherein the at least three states are defined bythe states of the first switch and the second switch.
 4. The lightingfixture of claim 1, wherein the first LED group provides light outputwhen the current provided by the first output channel is at the firstminimum level and the second LED group provides light output when thecurrent provided by the second output channel is at the second minimumlevel.
 5. The lighting fixture of claim 1, wherein the driver ispre-programmed to provide output current at the first minimum, firstinterim, and first maximum levels on the first output channel and ispre-programmed to provide output current at the second minimum, secondinterim, and second maximum levels on the second output channel based onthe state of the switching device.
 6. The lighting fixture of claim 1,wherein a combination of the current provided by the first outputchannel and the current provided by the second output channel issubstantially the same when the switching device is in any of the firststate, the second state, and the third state.
 7. A lighting fixture,comprising: a driver having a switch input, a first output channel, anda second output channel; a switching device connected to the switchinput of the driver, wherein the switching device provides at leastthree states; a first LED group configured to produce light output at afirst color temperature and connected to the first output channel; and asecond LED group configured to produce light output at a second colortemperature which is different than the first color temperature andconnected to the second output channel; wherein a state of the switchingdevice controls a first current provided to the first LED group via thefirst output channel and a second current provided to the second LEDgroup via the second output channel.
 8. The lighting fixture of claim 7,wherein the switching device includes a first switch and a second switchand the switch input of the driver includes a first switch input and asecond switch input, and the first switch is connected to the firstswitch input and the second switch is connected to the second switchinput.
 9. The lighting fixture of claim 8, wherein the first switch andthe second switch are two-position switches and wherein the switchingdevice is in a first state when the first switch is in a first positionand the second switch is in a second position; the switching device isin a second state when the first switch is in a second position and thesecond switch is in a first position; and the switching device is in athird state when the first switch is in the first position and thesecond switch is in the first position.
 10. The lighting fixture ofclaim 7, wherein the switching device includes at least a first state, asecond state, and a third state, and wherein a value of the firstcurrent is different in each of the three states and a value of thesecond current is different in each of the three states.
 11. Thelighting fixture of claim 10, wherein when the switching device is inthe first state, the first current is at a first maximum level and thesecond current is at a second minimum level; when the switching deviceis in the second state, the first current is at a first interim leveland the second current is at a second interim level; and when theswitching device is in the third state, the first current is at a firstminimum level and the second current is at a second maximum level. 12.The lighting fixture of claim 10, wherein a combined output of the firstoutput channel and the second output channel is substantially the samein each of the first state, the second state, and the third state. 13.The lighting fixture of claim 7, wherein the switching device includes acontroller, a first switch, and a second switch, and wherein the firstswitch is connected to a first input of the controller and the secondswitch is connected to a second input of the controller, and an outputof the controller is connected to the switch input of the driver. 14.The lighting fixture of claim 7, wherein the driver is pre-programmed toprovide output current at the first minimum, first interim, and firstmaximum levels on the first output channel and is pre-programmed toprovide output current at the second minimum, second interim, and secondmaximum levels on the second output channel based on the state of theswitching device.
 15. A lighting fixture, comprising: a multi-channeldriver having a switch input, and at least two output channels; aswitching device connected to the switch input of the multi-channeldriver, wherein the switching device provides at least three states; afirst LED group configured to produce light output at a first colortemperature and connected to a first output channel of the multi-channeldriver; and a second LED group configured to produce light output at asecond color temperature which is different than the first colortemperature and connected to a second output channel of themulti-channel driver; wherein a state of the switching device controls afirst current provided to the first LED group via the first outputchannel and a second current provided to the second LED group via thesecond output channel by controlling the multi-channel driver, andwherein a total current provided by the multi-channel driver on the atleast two output channels is substantially the same in each of the atleast three states of the switching device.
 16. The lighting fixture ofclaim 15, wherein the switching device includes a first switch and asecond switch and the switch input of the multi-channel driver includesa first switch input and a second switch input, and the first switch isconnected to the first switch input and the second switch is connectedto the second switch input.
 17. The lighting fixture of claim 16,wherein the first switch and the second switch are two-position switchesand wherein the switching device is in a first state when the firstswitch is in a first position and the second switch is in a secondposition; the switching device is in a second state when the firstswitch is in a second position and the second switch is in a firstposition; and the switching device is in a third state when the firstswitch is in the first position and the second switch is in the firstposition.
 18. The lighting fixture of claim 16, wherein when theswitching device is in a first state, the first current is at a firstmaximum level and the second current is at a second minimum level; whenthe switching device is in a second state, the first current is at afirst interim level and the second current is at a second interim level;and when the switching device is in a third state, the first current isat a first minimum level and the second current is at a second maximumlevel.
 19. The lighting fixture of claim 15, wherein the switchingdevice includes a controller, a first switch, and a second switch, andwherein the first switch is connected to a first input of the controllerand the second switch is connected to a second input of the controller,and an output of the controller is connected to the switch input of themulti-channel driver.
 20. The lighting fixture of claim 15, wherein themulti-channel driver is pre-programmed to provide output current at thefirst minimum, first interim, and first maximum levels on the firstoutput channel and is pre-programmed to provide output current at thesecond minimum, second interim, and second maximum levels on the secondoutput channel based on the state of the switching device.